For research use only.

Catalog No.S9681

MSA-2 Chemical Structure

CAS No. 129425-81-6

MSA-2 is an orally available non-nucleotide human STING agonist with antitumor activity.

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Biological Activity

Description MSA-2 is an orally available non-nucleotide human STING agonist with antitumor activity.
In vitro

MSA-2 in solution exists as monomers and noncovalent dimers in an equilibrium that strongly favors monomers; MSA-2 monomers cannot bind STING, whereas the noncovalent MSA-2 dimers bind STING with nanomolar affinity. MSA-2 exhibits substantially higher cellular potency in an acidified tumor microenvironment than normal tissue, owing to increased cellular entry and retention combined with the inherently steep MSA-2 concentration dependence of STING occupancy.[1]

In vivo

MSA-2 is orally available, manifesting similar oral and subcutaneous exposure in mice. In tumor-bearing mice, MSA-2 induced elevations of interferon-b in plasma and tumors by both routes of administration. Well-tolerated regimens of MSA-2 induced tumor regressions in mice bearing MC38 syngeneic tumors. In tumor models that are moderately or poorly responsive to PD-1 blockade, combinations of MSA-2 and anti-PD-1 antibody are superior in inhibiting tumor growth and prolonging survival over monotherapy.[1]


Cell Research:


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  • Cell lines: THP-1 cells, mouse macrophages
  • Concentrations: 20 μM, 0.16 μM-100 μM
  • Incubation Time: 5 h
  • Method:

    In the primary screen, THP-1 cells are incubated, in 1536-well plates, with test compounds (20 μM) in a RPMI1640-based assay medium in the presence of 5% carbon dioxide at 37°C for 5 hours. IFN-b levels are determined using an AlphaLISA assay and an EnVision Reader and expressed as percentages of IFN-b induced by cGAMP. STING binding activity of compounds is evaluated with a competitive radioligand binding assay using tritiated cGAMP and membrane embedded full-length recombinant human and mouse STING generated in insect cells. STING pathway activation by MSA-2 is assessed by Western blotting, probing phosphorylation status and total protein levels of STING, TBK-1, and IRF3 by using commercially available antibodies.

    (Only for Reference)
Animal Research:


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  • Animal Models: C57BL/6J mice, NSG mice, BALB/c mice, nude NCr mice
  • Dosages: 25 mg/kg, 40 mg/kg, 50 mg/kg, 60 mg/kg, 80 mg/kg, 160 mg/kg
  • Administration: intra tumor injection, SC, PO
    (Only for Reference)

Solubility (25°C)

In vitro DMSO 59 mg/mL (200.46 mM)
Ethanol 5 mg/mL (16.98 mM)
Water Insoluble

* Please note that Selleck tests the solubility of all compounds in-house, and the actual solubility may differ slightly from published values. This is normal and is due to slight batch-to-batch variations.

Chemical Information

Molecular Weight 294.32


CAS No. 129425-81-6
Storage powder
in solvent
Synonyms N/A

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Tech Support

Answers to questions you may have can be found in the inhibitor handling instructions. Topics include how to prepare stock solutions, how to store inhibitors, and issues that need special attention for cell-based assays and animal experiments.

Handling Instructions

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Cell Lines Assay Type Concentration Incubation Time Formulation Activity Description PMID